1. Field of the Invention
The present invention relates to quantization processing of pixel values of images, and more particularly, to image processing methods and devices capable of performing adaptive random number processing.
2. Description of the Prior Art
Quantization processing is a widely developed technique in image processing. For printers, half tone processing is a typical quantization processing method, where the half tone processing can be divided into two-level half tone processing and multilevel half tone processing according to the prior art.
The quantization processing mentioned above may cause quantization errors of pixel values of a quantized image according to many prior art methods. In order to prevent differences between the quantized image and the original image from being observed easily, issues related to distributing the quantization errors among neighboring pixels within the quantized image are widely discussed in the prior art. In general, such kinds of technologies can be referred to as error diffusion processing.
Please refer to FIG. 1. FIG. 1 is a diagram of four weighted values 7/16, 3/16, 5/16, and 1/16 utilized in an error diffusion method according to the prior art, where the error diffusion method is provided by Floyd and Steinberg. The arrows tells how quantization errors of a pixel P(i, j) are respectively distributed among its neighboring pixels P(i+1, j), P(i−1, j+1), P(i, j+1), and P(i+1, j+1) according to the weighted values 7/16, 3/16, 5/16, and 1/16 mentioned above, in order to adjust original values of the neighboring pixels P(i+1, j), P(i−1, j+1), P(i, j+1), and P(i+1, j+1) before the quantization processing for the neighboring pixel. If a printer prints a picture with gradient variations therein according to the error diffusion method mentioned above, the print out result typically has problems such as clustered points and even worm-like patterns, causing the print out quality to be unacceptable.